.child{
    border: 1px solid red;
    width: 400px;
    height: 200px;
    margin-bottom: 10px;
    display: flex;
}
.left{
    width: 200px;
    height: 200px;
    border: 1px solid orange;
    margin-right: 10px;
}
.detail{
     position: fixed;
     right: 100px;
     top: 100px;
     border: 1px solid skyblue;
     width: 200px;
     height: 200px;
}